Coil spool with protrusion to prevent wire migration

ABSTRACT

A wire holding device for, e.g., a coil used in a vehicle sensor, actuator, or ignition has a spool defining a winding bay that is bounded by opposed flanges of the spool. A wire support extends from flange to flange to define a winding surface, and a wire coil is wound in turns in the bay around the wire support. One or more protrusions are formed on the wire support and protrude above the winding surface for impeding lateral displacement of wires in the first layer of turns that lies against the surface of the wire support.

FIELD OF THE INVENTION

The present invention relates generally to spools that hold coil windings for vehicle components such as sensors, actuators, and ignition coils.

BACKGROUND OF THE INVENTION

Spools around which a wire is wound into a coil are in widespread use in vehicle applications. For instance, coils are used in vehicle actuators to, e.g., move hydraulic valves in automatic braking systems and other systems by means of the electromagnetic force induced by an energized coil acting on a ferromagnetic plunger or armature. Coils are also used in vehicle sensor applications to generate current when a sensor element moves nearby the coil, and of course the ignition system of a vehicle uses an ignition coil to provide combustion energy. Smart remote actuators (SRA) in diesel engine turbochargers also use coils.

As understood herein, it is often desired that orthocyclic (perfect) winding of the coil be effected. If a wire could be formed throughout its length with an exactly constant diameter, the distance between the flanges of the spool simply could be established to be exactly an integer number of wire diameters such that the integer number of turns would exactly and snugly fit between the flanges, thereby preventing lateral movement (and, hence, loss of orthocyclicity) of turns in a layer as succeeding layers are wound over them. In practice, however, making a wire that is potentially hundreds of meters in length with an exactly constant diameter throughout is not feasible. Consequently, wires have a nominal diameter that varies along the length of the wire within a tolerance range (diameter variance).

Accordingly, spools have been formed with grooves along the length of the wire support. More specifically, grooves can be formed, typically one per turn, in the cross-piece (“wire support”) that extends between the end flanges of the spool. Each groove receives a turn of the wire in the radially inmost layer of turns to confine it and thus prevent the turn from being laterally displaced when subsequent layers of the coil are successively wound on top of each other, exerting pressure on layers below. With the radially inmost layer of turns constrained, upper layers of turns likewise will be constrained by lower layers, promoting retention of the desired orthocyclic winding pattern.

As recognized herein, however, the groove design has drawbacks. Because grooves can be made only so small using feasible molding techniques, the smallest gauge of wire with which the groove technique can be used is at least as large as size 30 on the American Wire Gauge (AWG) scale. This is undesirable for applications that optimally would use wire of smaller diameter. Moreover, forming small grooves along the entire length of the wire support complicates the mold design and increases costs. With these critical recognitions in mind, the invention herein is provided.

SUMMARY OF THE INVENTION

A wire holding device includes a spool defining a winding bay. The winding bay is bounded by opposed flanges of the spool, and a wire support extends from flange to flange and defines a winding surface. A wire coil is wound in turns in the bay around the wire support. According to present principles, at least one protrusion is formed on the wire support and protrudes above the surface thereof for impeding lateral displacement of wires at least in a first layer of turns that lies against the surface of the wire support. Unlike the above-mentioned groove method, no portion of a wire is disposed radially inwardly from the surface of the wire support.

In non-limiting implementations the height of the protrusion above the surface of the winding bay is approximately one-third the diameter of a wire in the coil, a threshold lateral movement amount is about one-half the nominal diameter of a wire in the coil. In non-limiting implementations the number and spacing of protrusions is based on the desired threshold lateral movement amount and a wire diameter variance. Thus, the distance from one of the flanges and the first protrusion is an integer “N” number of coil turns, wherein “N” is established based on the desired threshold lateral movement amount and a wire diameter variance.

In another aspect, a wire holding device has a spool including a winding surface and a wire coil wound in turns around the winding surface. At least one protrusion is formed on the winding surface for impeding lateral displacement of wires at least in a first layer of turns that lies against the winding surface. The number and spacing of protrusions at least in part is based on a desired threshold lateral movement amount and a wire diameter variance.

In still another aspect, a spool for holding a coil of wire includes a wire support extending between two flanges and having at least one protrusion formed on a surface thereof.

The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a spool with coil according to the present invention, shown in an exploded relationship with a schematically-shown vehicle component; and

FIG. 2 is a longitudinal partial cross-section of the spool, showing only windings in the top portion of the bay with the windings in the bottom portion removed for clarity and showing a second protrusion in phantom.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIG. 1, a wire holding device is shown, generally designated 10, that includes a spool 12, preferably made of plastic, which is formed with opposed disk-shaped flanges 14. A coil 16 of wire is wound around the below-described wire support of the spool 12 within a winding bay defined between the flanges 14. The device 10 may be operably engaged in accordance with principles known in the art with a vehicle component 18. The component 18 may be, without limitation, a vehicle actuator, e.g., for moving a hydraulic valve in an automatic braking system or other system by means of the electromagnetic force induced by an energized coil 16 acting on a ferromagnetic plunger or armature. Or, the vehicle component 18 may be a vehicle sensor in which the coil 18, for instance, might generate current when a sensor element moves nearby the coil 18. Yet again, the coil 18 may be used as an ignition coil, or in a smart remote actuator (SRA) in a diesel engine turbocharger. Other industrial applications are contemplated hereunder.

Now referring to FIG. 2, a cross-section of a wire holding device generally labeled 10 is shown. The coil 16 of wire is shown as a cross section with numerous layers, four of which are shown in FIG. 2. A wire support 20 is centered on the spool flanges 14. The layer closest to the wire support 20 is an innermost layer 22 of the coil 16. Each succeeding layer moving outward from the wire support 20 is disposed between adjacent turns of the layer underneath. Accordingly, if, for example, the innermost layer 22 has fourteen turns, the next layer radially outward would have thirteen, and the next fourteen, and so on.

In the center of the innermost layer 22 a protrusion 24 is formed on the support 20. The protrusion 24 extends only partway around the circumference of the wire support 20, such as 330 degrees, so that the next turn of wire may alter course and lay flat without crossing on top of the protrusion 24. The wire support 20 typically is cylindrical as in FIG. 2. However, it need not be cylindrical; it could be rectangular, hexagonal, or other shape in transverse cross-section.

In non-limiting implementations the height of the protrusion 24 above the surface of the wire support 20 is about one-third the wire diameter, but it could be a little more or less. Preferably, the wire diameter is smaller than the diameter of size twenty eight gauge wire on the American Wire Gauge (AWG) scale because of the advantages afforded by the use of the protrusion, although this size is not limiting.

In FIG. 2, the protrusion 24 appears as trapezoidal shaped in cross-section. However, the protrusion 24 may be any shape or form as long as it prevents wire migration and prevents to adjacent turn from moving up the protrusion 24.

The number of protrusions and the spacing between them, including the distance from one of the flanges 14 and the first protrusion 24, is an integer “N” number of coil turns, wherein “N” is established at least in part based on a desired threshold maximum lateral movement amount and a wire diameter variance. To illustrate by example, if the wire nominal diameter is 1 millimeter, and the wire diameter varies by plus or minor one-tenth of a millimeter along the length of the wire, the total accumulated variation for any two turns may be as much as four-tenths of a millimeter. In one non-limiting embodiment, the threshold maximum lateral movement amount is one half of the diameter of the wire or 0.5 mm, so that in this example, every three turns would bring a maximum accumulated variation of 0.6 mm. Therefore, to ensure that the exemplary threshold maximum lateral movement limitation is never violated, a protrusion must be placed every two turns. This non-limiting example is illustrated by the additional protrusions shown in phantom in FIG. 2.

While the particular COIL SPOOL WITH PROTRUSION TO PREVENT WIRE MIGRATION as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and is thus representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more”. It is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. Absent express definitions herein, claim terms are to be given all ordinary and accustomed meanings that are not irreconcilable with the present specification and file history. 

1. A wire holding device, comprising: a spool defining a winding bay, the winding bay being bounded by opposed flanges of the spool, a wire support extending from flange to flange and defining a winding surface; a wire coil wound in turns in the bay around the wire support; and at least one protrusion formed on the wire support and protruding above the surface thereof for impeding lateral displacement of wires at least in a first layer of turns that lies against the surface of the wire support, wherein no portion of a wire is disposed radially inwardly from the surface of the wire support.
 2. The device of claim 1, wherein the height of the protrusion above the surface of the winding bay is approximately one-third the diameter of a wire in the coil.
 3. The device of claim 1, wherein the distance from one of the flanges and the at least one protrusion is an integer “N” number of coil turns, wherein “N” is established at least in part based on a desired threshold lateral movement amount and a wire diameter variance.
 4. The device of claim 1, comprising plural protrusions on the wire support and spaced longitudinally thereon, wherein the number and spacing of protrusions is at least in part based on a desired threshold lateral movement amount and a wire diameter variance.
 5. The device of claim 1, wherein the protrusion extends only part way around the wire support so that the next turn of wire may alter course and lay flat without without crossing on top of the protrusion.
 6. The device of claim 3, wherein the threshold lateral movement amount is about one-half the nominal diameter of a wire in the coil.
 7. A wire holding device, comprising: a spool including a winding surface; a wire coil wound in turns around the winding surface; and at least one protrusion formed on the winding surface for impeding lateral displacement of wires at least in a first layer of turns that lies against the winding surface, wherein the number and spacing of protrusions at least in part is based on a desired threshold lateral movement amount and a wire diameter variance.
 8. The device of claim 7, wherein no portion of a wire is disposed radially inwardly from the surface.
 9. The device of claim 7, wherein the height of the protrusion above the surface is approximately one-third the diameter of a wire in the coil.
 10. The device of claim 7, comprising plural protrusions on the wire support and spaced longitudinally thereon.
 11. The device of claim 7, wherein the protrusion extends only part way around the wire support so that the next turn of wire may alter course and lay flat without without crossing on top of the protrusion.
 12. The device of claim 7, wherein the threshold lateral movement amount is about one-half the nominal diameter of a wire in the coil.
 13. A spool for holding a coil of wire, comprising: a wire support extending between two flanges and having at least one protrusion formed on a surface thereof.
 14. The spool of claim 13, comprising a wire coil wound in turns around the surface, wherein the number and spacing of protrusions at least in part is based on a desired threshold lateral movement amount and a wire diameter variance.
 15. The spool of claim 13, wherein no portion of a wire is disposed radially inwardly from the surface.
 16. The spool of claim 14, wherein the height of the protrusion above the surface is approximately one-third the diameter of a wire in the coil.
 17. The spool of claim 13, comprising plural protrusions on the wire support and spaced longitudinally thereon.
 18. The spool of claim 14, wherein the protrusion extends only part way around the wire support so that the next turn of wire may alter course and lay flat without without crossing on top of the protrusion.
 19. The spool of claim 14, wherein the threshold lateral movement amount is about one-half the nominal diameter of a wire in the coil. 